CN110573287B

CN110573287B - Techniques for welding precipitation hardened superalloys using oscillating beams

Info

Publication number: CN110573287B
Application number: CN201780089822.3A
Authority: CN
Inventors: M.G.莫先科; M.V.梁赞诺夫
Original assignee: Siemens Energy Global GmbH and Co KG
Current assignee: Siemens Energy Global GmbH and Co KG
Priority date: 2017-04-19
Filing date: 2017-04-19
Publication date: 2022-08-02
Anticipated expiration: 2037-04-19
Also published as: EP3582921B1; WO2018194479A1; EP3582921A1; US20200070278A1; CN110573287A

Abstract

A technique for welding precipitation hardened superalloy (e.g., nickel-based superalloy) articles to produce a weld joint is presented. One or more portions are defined longitudinally throughout the length of the weld joint to be produced. Thereafter, superalloy material adjacent to the weld joint to be created is melted in one of the one or more portions by directing a power beam toward the portion and longitudinally oscillating the power beam within the portion. The intensity of the power beam and the oscillation frequency of the power beam are selected such that the superalloy material adjacent to the weld joint to be produced is uniformly heated and melted, thereby producing a weld joint from consolidation of the thus melted superalloy material. Thereafter, the weld joint is cured by gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the segment.

Description

Techniques for welding precipitation hardened superalloys using oscillating beams

The present invention relates to a technique for welding precipitation hardened superalloys, and in particular to a method and system for welding precipitation hardened superalloy articles to produce a weld joint.

Precipitation hardening, also known as precipitation strengthening or age hardening, is a well-known heat treatment technique used to increase the yield strength of ductile materials. Precipitation hardening may be advantageously used to increase the yield strength of many structural alloys (e.g., aluminum, magnesium, nickel, titanium, and alloys of certain steels and stainless steels). A specific example of the use of precipitation hardening is the working of superalloys, such as nickel-based alloys (Ni-based alloys), which are widely used for high-load parts of internal combustion engines and gas turbines due to their excellent mechanical properties and corrosion/oxidation resistance at high temperatures. A welding process is typically required when manufacturing and/or repairing the component.

The excellent mechanical properties of such precipitation hardened or precipitation strengthened materials or alloys are attributed to the presence of precipitation of secondary phases formed in the precipitation hardened or precipitation strengthened material or alloy, such as the presence of gamma prime (γ') phases in nickel-based superalloys that contribute to the precipitation strengthening of the material. The higher the amount of gamma prime phase in the precipitation hardened material or alloy, the higher the mechanical strength.

However, such precipitation hardened materials or superalloys, which include a relatively high content of secondary phase precipitates (e.g., the γ' phase in Ni-based superalloys), are prone to cracking during welding or during post-weld heat treatment. As a result, such precipitation hardened materials or superalloys are difficult to weld. When welding such precipitation hardened materials or superalloys (e.g., high strength nickel-based superalloys), two types of cracks can form: thermal cracking that occurs when the weld material solidifies during welding; and strain age cracking that occurs during the post-weld aging heat treatment.

Several techniques are currently used to improve the weldability of precipitation-hardened alloys, and in particular nickel-based superalloys. One known method of improving the weldability of nickel-base superalloys is to subject the material to a pre-welded overaging treatment. Conventional pre-welded overaging involves heating the material to solution temperature to dissolve the strengthening gamma prime phase, followed by slow cooling to re-precipitate the gamma prime phase as coarse particles. This increases the ductility of the material and thus helps to limit the build up of residual stresses caused by welding.

U.S. patent publication No. 5,509,980 a describes a pre-weld overaging heat treatment for nickel-based superalloys in which the alloy is heated to a solution temperature for a period of time sufficient to dissolve the gamma prime phase of the alloy microstructure and then slowly cooled during intermittent heating so that the gamma prime phase re-precipitates as coarse and equally large particles and the presence of fine-sized gamma prime phase particles is substantially avoided. The disclosure of U.S. patent publication No. 5,509,980 a further proposes a welding method in which the above-mentioned pre-welded overaging treatment is used.

U.S. patent No. 7,653,995 describes a method of weld repairing superalloy materials at ambient temperatures without causing cracking of the base material. In U.S. patent No. US 7,653,995, superalloy materials, such as CM-247 LC, are subjected to an overaged pre-weld heat treatment to increase the volume percent of gamma prime precipitation in the material to a level sufficient to allow ambient temperature welding without cracking. The CM-247 LC material was heated in a vacuum oven at a rate of about 0.5 ℃ per minute to an intermediate temperature of about 885 ℃. The material was then air-quenched to a temperature of about 52 ℃ to increase the gamma prime precipitation percentage to about 55%. U.S. patent No. 7,653,995 mentions that the material may then be fusion repair welded at ambient temperature using a filler material having a chemistry that matches that of the base material.

US patent US 6,333,484 describes a welding technique in which the entire weld area is preheated to a maximum ductility temperature range and this elevated temperature is maintained during welding and weld solidification.

The aforementioned techniques require a pre-welding process step, thus resulting in increased complexity, higher energy consumption, and extended manufacturing/maintenance process time. Accordingly, there is a need for techniques for welding precipitation hardened materials or alloys.

It is therefore an object of the present invention to provide a technique, and in particular a method and system for welding precipitation hardened materials or alloys, such as Ni-based superalloys. As previously described for the conventionally known techniques, it is desirable that the technique does not have any pre-welding heat treatment step, thereby being simpler and having a reduced manufacturing/maintenance process time. This technique is expected to be beneficial in reducing the risk of cracking and thereby improving the quality of the weldment.

The above objects are achieved by a method for welding a precipitation hardening superalloy article to produce a weld joint, and a system for welding a precipitation hardening superalloy article to produce a weld joint, having the following features:

a method for welding a precipitation hardened superalloy article to produce a weld joint, comprising:

-longitudinally defining one or more portions over the entire length of the welded joint to be produced;

-producing a weld joint by consolidating the so-melted superalloy material by directing a power beam towards and longitudinally oscillating the power beam within one of the so-defined one or more portions, thereby melting superalloy material adjacent the weld joint to be produced, wherein the intensity of the power beam and the oscillation frequency of the power beam are selected such that superalloy material adjacent the weld joint to be produced is uniformly heated and melted; and

-curing the weld joint, including gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion;

a system for welding a precipitation hardened superalloy article to produce a weld joint, the system comprising:

-a beam source for generating a power beam, wherein the beam source is configured to vary the intensity of the generated power beam;

-an oscillating mechanism configured to induce and/or modify oscillations of the power beam; and

-a control unit configured to:

-controlling the oscillating mechanism to oscillate the power beam longitudinally within one of the one or more portions at a selected frequency and controlling the beam source to provide a selected intensity of the power beam, wherein the selected intensity and the selected frequency are such that superalloy material adjacent to the weld joint to be produced is uniformly heated and melted, thereby producing the weld joint from consolidation of the thus melted superalloy material; and

-controlling the beam source to gradually decrease the intensity of the power beam from the selected intensity while controlling the oscillating mechanism to oscillate the power beam longitudinally.

In one aspect of the present technique, a method for welding a precipitation hardened superalloy article to produce a weld joint is presented. The precipitation hardened superalloy may be a nickel-based superalloy, such as a nickel-based superalloy having a volume percent of gamma prime phase equal to or greater than 45 volume percent.

In the method, one or more portions are defined longitudinally from the entire length of the weld joint to be produced. Subsequently, melting of the superalloy material adjacent to the weld joint to be produced is performed in one or more sections. Melting is performed by directing a power beam toward and longitudinally oscillating the power beam within the portion. The power beam is generated by a beam source, such as a laser beam welding beam source (e.g., a laser emitter), an electron beam welding beam source (e.g., an electron gun). The power beam is longitudinally oscillated in the section by oscillating the beam source generating the power beam or by oscillating the beam itself while keeping the beam source generating the power beam stationary, or by a combination of oscillating the power beam and oscillating the beam source. The intensity of the power beam and the frequency of oscillation of the power beam are selected such that the superalloy material adjacent to the weld joint to be produced is uniformly heated and melted, thereby producing a weld joint from consolidation of the thus melted superalloy material. As used herein, the term "consolidating" includes the acts of forming a mass or whole together, or combining and then solidifying.

In the present disclosure, the phrase "oscillation of the power beam" or "oscillation of the beam" refers to changing the direction of the beam by physically moving the beam source or by keeping the beam source fixed and changing the direction of the beam.

Thereafter, in the method, the weld joint is cured by gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion. In gradually reducing the intensity of the power beam while longitudinally oscillating the power beam in the portion, the oscillation frequency of the power beam may be the same as the oscillation frequency of the power beam when melting the superalloy material in the vicinity of the weld joint to be produced. Further, in gradually reducing the intensity of the power beam while longitudinally oscillating the power beam in the portion, the intensity of the power beam may be gradually reduced while longitudinally oscillating the power beam in the portion until the temperature of the weld joint reaches between 600 ℃ and 700 ℃.

The present technique does not require any pre-weld heat treatment steps or any other steps resulting from any pre-weld heat treatment steps, thereby allowing for reduced energy consumption and reduced manufacturing/repair process time. By using an oscillating power beam during solidification of the weld joint and an appropriate strength of the power beam, the present technique allows for a reduction in the cooling rate, which in turn will result in lower γ/γ 'lattice mismatch and lower internal stresses at the interface between the γ' particles and the γ matrix in the microstructure of the superalloy. Reducing internal stresses is beneficial to reducing the risk of cracking, thereby improving the quality of the weldment.

In one embodiment of the method, when a plurality of sections are defined longitudinally from the entire length of the weld joint to be produced, melting of the superalloy material is performed separately for the different sections to produce the weld joint and solidify the weld joint. The length of each portion thus defined is between 10mm and 100 mm.

In another aspect of the present technique, a system for welding a precipitation hardened superalloy article to produce a weld joint is presented. The system includes a beam source, an oscillation mechanism, and a control unit. The beam source generates a power beam. The beam source is configured to vary the intensity of the generated power beam, i.e. to reach a desired power beam intensity, and to increase and/or decrease the intensity from the desired intensity. The beam source may be a laser beam welding beam source or an electron beam welding beam source. The oscillation mechanism induces and/or modifies the oscillation of the power beam.

The control unit longitudinally defines one or more portions throughout the length of the weld joint to be produced. The control unit controls the oscillation mechanism to effect longitudinal oscillation of the power beam at the selected frequency within one of the one or more sections and controls the beam source to provide the power beam at the selected intensity. The strength selected and the frequency selected are such that the superalloy material adjacent to the weld joint to be produced is uniformly heated and melted, thereby producing a weld joint from consolidation of the so-melted superalloy material.

Further, the control unit controls the beam source to gradually decrease the intensity of the power beam from the selected intensity while controlling the oscillation mechanism to longitudinally oscillate the power beam. In a related embodiment of the system, the control unit controls the beam source to gradually decrease the intensity of the power beam from the selected intensity while controlling the oscillating mechanism to longitudinally oscillate the power beam at the selected frequency.

In an embodiment of the system of the present technology, the control unit longitudinally defines one or more sections, each section having a length so defined as to be between 10mm and 100 mm.

In a further embodiment of the system, the oscillation mechanism causes and/or changes the oscillation of the power beam by causing and/or changing an oscillation in the beam source or by repeatedly changing the direction of movement of particles (e.g. electrons) forming the power beam or by both.

In another embodiment of the system, the control unit further controls the oscillating mechanism to stop longitudinally oscillating the power beam when the temperature of the weld joint as detected by the temperature sensor reaches between 600 ℃ and 700 ℃ while gradually reducing the intensity of the power beam.

The present technology will be further described hereinafter with reference to the illustrated embodiments shown in the drawings, in which:

FIG. 1 schematically illustrates an exemplary embodiment of a system for welding precipitation hardened superalloy articles to produce a weld joint, in accordance with aspects of the present technique;

FIG. 2 graphically illustrates the effect of cooling rate on calculated γ/γ' lattice mismatch for a CM-247 LC superalloy; and

FIG. 3 shows a flow chart representing a method according to the present technique.

The above and other features of the present technology are described in detail below. Various embodiments are described with reference to the drawings, wherein like reference numerals are used to refer to like elements throughout. In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It should be noted that the illustrated embodiments illustrate rather than limit the invention. It may be evident that such embodiment(s) may be practiced without these specific details.

It may be noted that in the present disclosure, the terms "first," "second," and the like are used herein only to facilitate discussion, and unless otherwise noted, do not have a particular temporal or chronological meaning.

The present invention provides a technique for welding precipitation hardened superalloy articles to produce a weld joint. The precipitation hardened superalloy may be a nickel-based superalloy, for example, having a volume percent of gamma prime phase equal to or greater than 45 volume percent. A specific example of a precipitation hardened superalloy is the Directionally Solidified (DS) cast nickel-based superalloy material sold under the name CM-247 LC by Cannon-Muskegon Corporation. CM-247 LC is known to have the following nominal composition, expressed in weight percent: 0.07% of carbon; 8% of chromium; 9% of cobalt; 0.5 percent of molybdenum; 10% of tungsten; 3.2% of tantalum; 0.7 percent of titanium; 5.6 percent of aluminum; 0.015% of boron; 0.01 percent of zirconium; 1.4% of hafnium; and the remainder nickel. The article made from the precipitation hardened superalloy, hereinafter referred to as a superalloy, may be a component of a gas turbine, such as a blade or vane of a gas turbine or any other component of a turbine subject to hot gas flow in the gas turbine (e.g., a heat shield). The present technique is used to weld such articles. In the welding, a suitable filler material, for example, a filler material for CM-247 LC (Mar-M247) may be used as a base material.

One of the key parameters when considering the tendency for cracks to occur in high volume fractions of precipitation-strengthened alloys (e.g., nickel-based superalloys having 45 volume percent or greater of the γ' phase), is the lattice mismatch value between the precipitation and alkali metal phases. In nickel-based superalloys, the larger gamma/gamma prime (γ/γ') lattice mismatch can create internal misfit stresses at the interface between the gamma prime particles and the metallic gamma matrix that, in combination with thermally induced (tensile) stresses created during solidification of the weld, can lead to microcracking of the welded material. Therefore, it is advantageous to minimize the major gamma/gamma mismatch in terms of preventing the risk of cracking.

As can be seen from fig. 2, the magnitude of the gamma/gamma 'lattice mismatch is strongly dependent on the cooling rate during solidification, i.e. the lower the cooling rate of the weld joint, the smaller the gamma/gamma' lattice mismatch and the smaller the risk of weld cracking. FIG. 2 graphically illustrates the effect of cooling rate on the calculated gamma/gamma 'lattice mismatch for a gamma' portion of about 60 volume percent of alloy CM-247 LC. This desired lower cooling rate for the weld joint, and more specifically for the weld, is achieved by the present technique. In FIG. 2, axis 80 represents the γ/γ' lattice mismatch and axis 90 represents the cooling rate in deg C/s (degrees Celsius per second).

In the following, the steps of the method 100 of the present technology and the system 1 according to aspects of the present technology as shown in fig. 3 are explained with reference to fig. 1. The present technique is used to weld precipitation-hardened superalloys, which are hereinafter referred to simply as superalloys.

A system 1 for welding precipitation hardened superalloy articles to produce a weld joint 5 is presented. In the exemplary embodiment of fig. 1, the two parts, part 2 and part 3, are intended to be welded together. The

portions

2, 3 may be parts of the same item, for example one portion may be a broken portion or a substitute for the heat shield, while the other portion may be the remaining body of the heat shield. The

parts

2, 3 may be two different articles welded to each other. As shown in fig. 1, the

parts

2, 3 are intended to be welded to each other, and it is therefore desirable to produce a welded joint 5. The weld joint 5 may be produced by welding the

components

2, 3 to each other, with or without a suitable filler material. The

parts

2, 3 or at least the areas of the

parts

2, 3 adjacent to the weld joint 5 to be produced are formed from a superalloy. The weld joint 5 to be produced between the

parts

2, 3 has been indicated by the dashed line 5.

As shown in fig. 1, the weld joint 5 to be produced is divided into one or more sections 7. It may be noted that for a better understanding, three short line segments are used on the weld joint 5 to delimit the two portions 7, however, in the application of the present technique, such visual delimitation is not required. It may also be noted that only two portions 7 are shown in fig. 1, however, it will be appreciated by a person skilled in the art that several such portions 7 are possible depending on the overall length or length of the weld joint 5 to be produced and the length of the portions 7. In one embodiment of the present technique, the length of each such portion 7 is between 10mm and 100 mm. The present technique is applied to each portion 7 separately and independently of the remainder of the portion 7. For example, the present technique may be applied to one of the portions 7, and then after the present technique is summarized for that portion 7, it may be subsequently applied to an adjacent portion 7, and then to another portion 7. In another example, the present techniques may be applied to multiple portions 7 simultaneously, and then, after the present techniques are summarized for one or more such portions 7, they may be subsequently applied to one or more adjacent portions 7. The entire length of the weld joint 5 is only welded when all sections 7 have been subjected to the present technique.

The system 1 comprises a beam source 10, an oscillating mechanism 20 and a control unit 30. The beam source 10 generates a power beam. In fig. 1, the points 12 are depicted as schematically representing the power beams impinging on the

components

2, 3 and the weld joint 5 to be produced. For purposes of illustration, the present technique is described below with respect to portion 7 of FIG. 1 having points 12 therein. The beam source 10 may be a laser beam welding beam source or an electron beam welding beam source. The beam source 10 is configured to vary the intensity of the generated power beam, i.e. to reach a desired intensity of the power beam, and to increase and/or decrease the intensity from the desired intensity. The beam source 10 for welding superalloys, and more particularly the beam sources used in electron beam welding and laser beam welding, and the mechanisms and techniques for varying the intensity of such beam sources, are well known in the welding art and, therefore, are not explained in further detail herein for the sake of brevity.

The oscillating mechanism 20 induces and/or modifies the oscillation of the power beam. This is achieved by causing and/or varying the oscillation of the beam source 10, or by causing and/or varying the oscillation of the beam generated by the beam source 10, or by a combination thereof. The oscillating mechanism 20 may comprise a motor, a variable frequency drive, a motor controller, etc., to enable introduction and variation of the oscillation of the beam source 10. Instead of or in addition to the above-described structure of the oscillating mechanism 20, the oscillating mechanism 20 may comprise a system or arrangement (not shown) of electromagnetic lenses or also called magnetic lenses. When the beam source is an electron gun, the electromagnetic lens is focused and/or deflected, so that an oscillation can be performed that moves the charged particles (e.g. electrons forming an electron beam). The charged particles that make up the electron beam are deflected from one direction to another by the lorentz force, making it possible for the power beam to move back and forth along a given axis.

Electromagnetic lenses typically comprise several electromagnets arranged in a quadrupole, hexapole or higher format, i.e. electromagnetic coils placed at the vertices of a square or other regular polygon. By this configuration, a tailored magnetic field can be created to manipulate the particles, i.e. to form electrons of the power beam, thereby manipulating or changing the direction of the beam. In an exemplary embodiment of the system 1, the beam source 10 is a laser emitter, and the oscillation mechanism 20 includes a driver that physically moves the laser emitter to cause oscillation of the laser beam. In another embodiment, the beam source 10 is an electron gun and the oscillation mechanism 20 comprises an electromagnetic lens system that moves electrons of the power beam to cause oscillation of the beam without physically oscillating the electron gun.

As described above, the oscillation mechanism 20 controls or acts on the power beam or beam source 10 to initiate oscillation of the power beam and/or beam source 10, to stop oscillation of the power beam and/or beam source 10, to increase or decrease oscillation of the power beam and/or beam source 10, and/or to maintain oscillation of the power beam and/or beam source 10 at a desired frequency. The oscillating mechanism 20 also functions to limit the oscillation of the power or beam source 10 so that the spot 12 remains within the portion 7 on which the present technique is being performed. The oscillation is performed in a direction 9 extending longitudinally along the portion 7.

The control unit 30 longitudinally defines one or more portions 7 from within the entire length of the weld joint 5 to be produced. The entire length of the weld joint 5 may be provided to the control unit 30 manually by the user, or may be determined by the control unit 30 based on a pointer provided by the user to indicate at least two positions between which the weld joint 5 is to be produced.

The control unit 30 controls the oscillating mechanism 20 to effect longitudinal oscillation of the power beam at the selected frequency within the one or more portions 7 and controls the beam source 10 to provide the selected power beam intensity. The strength selected and the frequency selected are such that the superalloy material adjacent to the weld joint 5 is uniformly heated and melted, resulting in a weld joint 5 from consolidation of the thus melted superalloy material.

Further, the control unit 30 controls the beam source 10 to gradually decrease the intensity of the power beam from the selected intensity, while controlling the oscillation mechanism 20 to longitudinally oscillate the power beam. The beam source 10 and/or the power beam may be oscillated at a uniform frequency or the same frequency (i.e., a selected frequency) by the oscillating mechanism 20 during melting and subsequently during solidification of the weld joint 5.

Hereinafter, the steps of the method 100 of the present technique will be further explained with reference to fig. 3. The method 100 of the present technology may be implemented by the system 1 of the present technology. In the method 100, as described above, one or more portions 7 are longitudinally defined in step 110 from the entire length of the weld joint 5 to be produced. The remaining steps of the method 100 are performed on one of the portions 7. Subsequently, the superalloy material within the one portion 7 and adjacent to the weld joint 5 to be produced is melted in step 120. Melting is performed by directing a power beam towards the portion 7 and longitudinally oscillating the power beam within the portion 7. The intensity of the power beam and the oscillation frequency of the power beam are chosen such that the superalloy material within the portion 7 and adjacent to the weld joint 5 to be produced is uniformly heated and melted, so that the weld joint 5 is produced by consolidation of the superalloy material thus melted.

Due to the uniform heating, the temperature of the part of the section 7 or the sub-part of the section 7 is uniformly or substantially similarly increased, thereby avoiding the formation of substantial thermal gradients within the sub-part of the section 7. Two sub-regions or zones within the portion 7 are said to be "uniformly" heated if the temperature difference between the two sub-portions or zones is in the range of zero and 50 degrees celsius at any given point in time during the melting of the superalloy material within the portion 7.

Thereafter, in the method 100, the weld joint 5 is cured in step 130 by gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion 7. The phrase "taper" as used herein means decrease at a uniform or consistent rate, or continuously or steadily, or uninterruptedly or continuously, or non-abruptly or non-accidentally. In gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion 7, the oscillation frequency of the power beam may be the same as the oscillation frequency of the power beam maintained when the superalloy material is melted in the previous step. Further, in gradually decreasing the intensity of the power beam while longitudinally oscillating the power beam in the portion, the gradually decreasing the intensity of the power beam while longitudinally oscillating the power beam in the portion may be performed until the temperature of the weld joint 5 reaches between 600 ℃ and 700 ℃. After the temperature of the weld joint 5 reaches between 600 ℃ and 700 ℃ during cooling or solidification, the beam source 10 can be switched off, i.e. no further requirement of a power beam is required for this portion 7. Furthermore, the oscillation of the beam source 10 and/or the power beam may also be stopped. Since the power beam does not impinge further on the weld joint 5 in this portion 7, the weld joint 5 in the portion 7 is thereafter cooled naturally by convection with the surrounding air or environment.

It may be noted that although the system 1 of the present technology and the method 100 of the present technology have been described above for welding the weld joint 5 with respect to one portion 7, the system 1 and the method 100 may be used to weld the weld joint 5 with respect to a plurality of portions 7 at the same time. In order to perform welding of a plurality of portions 7 simultaneously, the system 1 will comprise: a plurality of beam sources 10 or one beam source 10 accompanying a beam splitter; an oscillating mechanism 20 associated with each of the plurality of beams or the split beam; and a control unit 30 having one or more processors or processing modules to control the one or more beam sources 10 and/or to control the one or more oscillation mechanisms 20.

while the technology has been described in detail with reference to certain embodiments, it is to be understood that the technology is not limited to those precise embodiments. On the contrary, many modifications and variations are possible to those skilled in the art in light of the present disclosure describing exemplary modes of carrying out the invention without departing from the scope and spirit of the invention. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes, modifications and variations that fall within the meaning and range of equivalency of the claims are to be embraced within their scope.

List of reference numerals

1 System

2 parts of articles

3 parts of articles

5 welded joint to be produced

7 part (C)

9 longitudinal direction

10 beam source

20 oscillating mechanism

30 control unit

80 represents the axis of major gamma/gamma mismatch

Cooling rate of 90 in degrees centigrade per second

100 method

110 define one or more portions

120 melting

130 curing

Claims

1. A method (100) for welding a precipitation hardened superalloy article to produce a weld joint (5), the method comprising:

-longitudinally defining (110) one or more portions (7) over the entire length of the welded joint (5) to be produced;

-melting (120) the superalloy material adjacent to the weld joint (5) to be produced by directing a power beam towards one of the one or more portions (7) so defined and longitudinally oscillating the power beam within the portion (7), wherein the intensity of the power beam and the oscillation frequency of the power beam are selected such that the superalloy material adjacent to the weld joint (5) to be produced is uniformly heated and melted, thereby producing the weld joint (5) from consolidating the superalloy material so melted; and

-solidifying (130) the weld joint (5), comprising gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion (7).

2. The method (100) according to claim 1, wherein the melting (120) of the superalloy material is performed separately for different portions (7) to produce the weld joint (5) and solidify (130) the weld joint (5).

3. A method (100) according to claim 1 or 2, wherein the length of each of said portions (7) thus defined is between 10mm and 100 mm.

4. The method (100) according to any one of claims 1 to 3, wherein the power beam is longitudinally oscillated within the portion (7) by one of oscillating a beam source (10) generating the power beam, maintaining the power beam oscillation while the beam source (10) is fixed in position, and simultaneously oscillating the power beam and the beam source 10.

5. The method (100) according to any one of claims 1 to 4, wherein the power beam is generated by one of a laser beam welding beam source and an electron beam welding beam source.

6. The method (100) according to any one of claims 1 to 5, wherein, in the process of gradually reducing the intensity of the power beam while longitudinally oscillating the power beam within the portion (7), the oscillation frequency of the power beam is the same as the oscillation frequency of the power beam when melting the superalloy material adjacent to the weld joint (5) to be produced.

7. The method (100) according to any of claims 1 to 6, wherein the tapering of the intensity of the power beam while longitudinally oscillating the power beam within the portion (7) is performed until the temperature of the weld joint (5) within the portion (7) reaches between 600 ℃ and 700 ℃ in the process of tapering the intensity of the power beam while longitudinally oscillating the power beam within the portion (7).

8. The method (100) according to any one of claims 1 to 7, wherein the precipitation hardened superalloy is a nickel-based superalloy.

9. The method (100) of claim 8, wherein the nickel-base superalloy is a nickel-base superalloy having a gamma prime phase volume percent equal to or greater than 45 volume percent.

10. A system (1) for welding a precipitation hardened superalloy article to produce a weld joint (5), the system (1) comprising:

-a beam source (10) for generating a power beam, wherein the beam source (10) is configured to vary the intensity of the generated power beam;

-an oscillating mechanism (20) configured to induce and/or modify oscillations of the power beam; and

-a control unit (30) configured to:

-longitudinally defining one or more portions (7) over the entire length of the welded joint (5) to be produced;

-controlling the oscillating mechanism to oscillate the power beam longitudinally within one of the one or more portions (7) at a selected frequency and controlling the beam source (10) to provide a selected intensity of the power beam, wherein the selected intensity and the selected frequency are such that the superalloy material adjacent to the weld joint (5) to be produced is uniformly heated and melted, thereby producing the weld joint (5) from consolidation of the thus melted superalloy material; and

-controlling the beam source (10) to gradually decrease the intensity of the power beam from the selected intensity while controlling the oscillating mechanism to oscillate the power beam longitudinally.

11. The system (1) according to claim 10, said control unit (30) being further configured to longitudinally define said one or more portions (7), the length of each of said portions (7) being thus defined between 10mm and 100 mm.

12. The system (1) according to claim 10 or 11, wherein the oscillation mechanism (20) is configured to cause and/or vary the oscillation of the power beam by causing and/or varying one of the oscillations in the beam source (10), by causing and/or varying the oscillation in the power beam while keeping the beam source (10) fixed in position, and by causing and/or varying the oscillation in the power beam and the beam source 10 simultaneously.

13. The system (1) according to any one of claims 10 to 12, wherein the beam source (10) is one of a laser beam welding beam source and an electron beam welding beam source.

14. The system (1) according to any one of claims 10-13, wherein the control unit (30) is further configured to:

-controlling the beam source (10) to gradually decrease the intensity of the power beam from the selected intensity while controlling the oscillating mechanism (20) to longitudinally oscillate the power beam at the selected frequency.

15. The system (1) according to any one of claims 10-14, wherein the control unit (30) is further configured to:

-controlling the beam source (10) to stop generating the power beam and/or

-controlling the oscillating mechanism (20) to stop oscillating the power beam when the temperature of the weld joint (5) reaches between 600 ℃ and 700 ℃ while gradually reducing the intensity of the power beam.